1. Field of the Invention
The present invention relates generally to a mobile communication terminal, and in particular, to an apparatus and a method for scanning Home Public Land Mobile Network (Home PLMN) in a mobile communication terminal.
2. Description of the Related Art
Mobile communication terminals no longer have a service area limited within a network, as they support a roaming service and can use mobile communication in any part of the world just like in a single network. The Public Land Mobile Network (PLMN) enables mobile communication service providers to provide roaming of the telecommunications service, and mainly includes a Base Transceiver Subsystem (BTS), a subscriber location registration device and a mobile communication exchanger. The Home Public Land Mobile Network (Home PLMN) is the PLMN registered by the user to receive service of a certain service provider.
The second, or the third generation mobile communication systems provided by the European Telecommunications Standards Institute (ETSI) or the 3rd Generation Partnership Project (3GPP) suggest that a mobile communication terminal periodically scan the Home PLMN based on the Home PLMN scanning time stored in the Subscriber Identity Module (SIM), if the mobile communication terminal receives service via the Visitor Public Land Mobile Network (VPLMN), instead of the Home PLMN. Simply, the mobile communication terminal carries out Home PLMN searching periodically, by scanning the Home PLMN if the scanning timer expires, and starting the scanning timer if the Home PLMN scanning is finished.
If the scanning timer expires, the periodical Home PLMN searching is carried out only in an idle mode of the mobile communication terminal, that is, the periodic Home PLMN searching is not carried out in a non-idle mode in which the mobile communication terminal is transmitting data or Short Message Service (SMS), or conducting a call. The mobile communication terminal does not attempt the Home PLMN searching if the Home PLMN scanning timer expires during the transmission of SMS or data, or conducting of a call, but instead starts the Home PLMN scanning timer. If this situation continues, there will not be an attempt to search the Home PLMN for a considerable length of time, and accordingly, the mobile communication terminal is left in the VPLMN even where there is a home PLMN available.